In particular, it is advantageously used for bags for granular foods, such as dog or cat biscuits, for example.
Granular food bags made out of two main walls and two side faces are already known, these walls and faces being made of a flexible-sheet type material, the two main walls being assembled, at their two ends, the one on top of the other along two respective assembly lines, each assembly line being, for example, a weld or glue line, the two side faces, for their part, being shaped in the form of a gusset.
The walls and the side faces can be realised in any flexible material, for example with a base made of paper, flexible cardboard, plastic sheets or light metal. It is also possible to form laminated multilayered sheets using more than one of these materials.
FIGS. 1a to 1c represent diagrammatically the three main stages in the manufacture of an example of such a bag, according to the prior art.
In these figures, a sheet 10 realised in a flexible material is firstly doubled over along a median line L (FIG. 1a), such as to form the two main walls 11, 12 of the bag.
The line L is orientated in a direction corresponding to the direction which will be the direction of principal extension of the bag once this has been made.
The sheet 10 having thus been doubled over, the two main walls 11, 12 are joined together in such a way as to form a substantially cylindrical sleeve C (FIG. 1b). This “joining together” can be effected by any means which is known per se and is suited to the sheet material (welding, gluing . . . )
In the formation of this sleeve C, at the level of the side edges of the two walls 11 and 12 gussets S are formed by the arrangement of a fold line LS over all or part of the sleeve height (corresponding to the height of the bag) on each side of each main wall.
It is pointed out that, within the introduction of the present text, all terms of orientation (“below”, “above”, “upper”, “lower”, etc.) must be understood in relation to an arrangement in which the bag is held upright by being placed by its bottom on a horizontal surface, as represented in FIG. 1c. 
The bag is then closed at the level of the lower and upper ends of the sleeve, for example by two weld lines L1 and L2. The bag is filled prior to the closure of the second of these lines.
A bag of simple design is thus obtained, made up of two main walls 11 and 12, the side edges of which are joined by gussets S.
It is also possible to form an equivalent bag in a different way, for example by fitting together a plurality of separate sheets.
The bags such as described above are extremely widely used to contain potentially runny foods, for example to contain animal foods (and, more especially, granular foods).
Bags of reduced dimensions (containing up to about six kilograms of product) generally appear as in FIG. 1c. 
These bags are generally intended to be handled when they are in the upright position, corresponding to the representation shown in FIG. 1c. In this position, their direction of principal extension is vertical.
In the case of larger sized bags, it is necessary additionally to provide gripping means, such as handles which are added onto the bag. Such handles are fixed on the bag at its upper end.
A first drawback of this known configuration is that the bag must be handled in the upright position: the handling of the bag can then prove difficult, especially in the case of large-sized bags. Moreover, the stability of the vertically stored bag is not guaranteed.
And since extra material is needed to form such add-on handles, these give rise to an additional cost, which, in itself, constitutes another drawback.
Moreover, the addition of such handles onto the bag requires an extra stage to be realised in the bag manufacturing process.
The object of the invention is to propose a bag which enables the above mentioned drawbacks to be eliminated.
In order to achieve this object, the invention proposes a bag assembly for foods, in particular granular foods, including at least one bag which comprises two main walls joined by two side faces forming a gusset along each side edge of the said main walls, and gripping means for the bag assembly, characterised in that the gripping means are implanted close to a side edge of each bag of the assembly.